scholarly journals Packaging Design, Weld Fatigue analysis and Validation of Diesel Exhaust After-treatment System

2018 ◽  
Vol 8 (2) ◽  
pp. 36
Author(s):  
Sonal Nareddiwar ◽  
Tapobrata Dey ◽  
R. Sunilkumar
Keyword(s):  
Fatigue Life ◽  
Fatigue Failure ◽  
Welded Joints ◽  
Diesel Exhaust ◽  
Bending Moment ◽  
Fatigue Analysis ◽  
Treatment System ◽  
Packaging Design ◽  
Weld Fatigue ◽  
Exhaust After Treatment

Diesel exhaust after treatment system is usually designed to meet stringent packaging constraints and emission norms. After treatment packaging has critical impact on the overall system efficiency and durability since many components in exhaust systems have welded joints. An after treatment inlet and outlet tube joints, connected to engine outlet and Original Equipment Manufacturer (OEM) tailpipe respectively are subjected to vibrations and bending moment leading to fatigue failure at the inlet/outlet welded joints. It has been observed over the years that the prevailing failure modes in after treatment systems are cracked welds at joints between inlet tubes and flanges, outlet tubes and connecting tailpipes. Fatigue failure is a complex and progressive form of local damage which occurs in welded components of exhaust after-treatment systems. Thus, this fatigue failure needs to be estimated accurately and at the early stage of design to save cost and time. But due to geometrical irregularities, compact packaging design and load transfer conditions, it becomes difficult to estimate accurate fatigue strength of the welded areas. Thus weld fatigue analysis, a high cycle fatigue test to validate inlet/outlet module of exhaust system against dynamic overturning bending moment and to calculate the location of minimum weld fatigue life within the inlet welded joints is performed. Weld fatigue analysis uses advanced fatigue assessment technique, BS 7608, Stress x Life (S x N) approach for accurate and precise estimation of welds. The present work deals with reducing the package volume of the after treatment system by applying different concepts, verifying design robustness by FEA simulation using ANSYS 18.2 and validating the structural durability of the system by testing. The objective of the present work is to estimate the fatigue life of the welded structures precisely and accurately, calculate the threshold bending moment to determine whether the design is robust to the bending moment loads seen over course of its life and make design modifications as per simulation result. Further the FEA and testing results of weld fatigue analysis are correlated.

Weld Rod Fatigue Analysis Using Effective Notch Stress Method

2018 ◽  
Author(s):  
Kumarswamy Karpanan ◽  
Allison Weber Kirk ◽  
Gerald Hershman
Keyword(s):  
Fatigue Life ◽  
Welded Joints ◽  
Failure Modes ◽  
Welding Process ◽  
Fatigue Analysis ◽  
Fillet Welds ◽  
Notch Stress ◽  
Effective Notch Stress ◽  
Weld Fatigue ◽  
Weld Root

Welds are one of the commonly used joint types and are employed extensively in subsea oil and gas production equipment. Commonly used weld joints in subsea components are fillet, butt, full-penetration, plug, and girth. Fatigue is one of the critical failure modes for welded joints. Welded joints are complex to analyze for fatigue loading due to the microstructure change during the welding process. The welding process also induces residual stress in the heat affected zone (HAZ) surrounding the weld. This, in turn, can adversely affects the fatigue life of the joint. The S-N fatigue approach is commonly used for weld fatigue analysis due to the simplicity of this method. Industry standards such as DNV, IIW, BS-7608, and ASME BPVC Sec VIII Div. -2 or -3 are typical references for this type of analysis. For subsea specific applications, DNV-RP-C203 and BS-7608 are generally used because these two standards provide S-N curves for welds in “air” as well as in “seawater with cathodic protection”. These two codes also provide S-N curves for various weld geometries ranging from simple fillet welds to complex tubular joints. Some of the weld fatigue analysis techniques used in the subsea industry are the: nominal stress approach, structural hot spot stress approach, effective notch stress approach (ENS), structural stress method (ASME VIII-2, -3) and the Fracture mechanics based fatigue crack propagation (FCG) approach. This paper presents the fatigue analysis of fillet welds in bore inserts using the ENS method. In the ENS method, a 1mm radius notch is modelled at the weld root or toe, see Figure 1, which yields a finite weld root stress. The stress analysis is carried out using FEA and the stresses on the notch along with the appropriate fatigue curve are used to estimate the weld root fatigue life.

scholarly journals A Multi-Scale Submodel Method for Fatigue Analysis of Braided Composite Structures

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4190
Author(s):  
Jincheng Zheng ◽  
Peiwei Zhang ◽  
Dahai Zhang ◽  
Dong Jiang
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Fatigue Failure ◽  
Failure Criterion ◽  
Cell Model ◽  
Fatigue Analysis ◽  
Analysis Method ◽  
Shear Lag ◽  
Multi Scale ◽  
Meso Scale

A multi-scale fatigue analysis method for braided ceramic matrix composites (CMCs) based on sub-models is developed in this paper. The finite element shape function is used as the interpolation function for transferring the displacement information between the macro-scale and meso-scale models. The fatigue failure criterion based on the shear lag theory is used to implement the coupling calculation of the meso-scale and micro-scale. Combining the meso-scale cell model and the fatigue failure criterion based on the shear lag theory, the fatigue life of 2D SiC/SiC is analyzed. The analysis results are in good agreement with the experimental results, which proves the accuracy of the meso-scale cell model and the fatigue life calculation method. A multi-scale sub-model fatigue analysis method is used to study the fatigue damage of 2D SiC/SiC stiffened plates under random tension–tension loads. The influence of the sub-models at different positions in the macro-model element on the analysis results was analyzed. The results shows that the fatigue analysis method proposed in this paper takes into account the damage condition of the meso-structured of composite material, and at the same time has high calculation efficiency, and has low requirements for modeling of the macro finite element model, which can be better applied to the fatigue analysis of CMCs structure.

A Fatigue Failure Mechanism of Welded Piping Joints

2005 ◽  
Author(s):  
Tasnim Hassan ◽  
Xiangyang Lu
Keyword(s):  
Residual Stresses ◽  
Fatigue Failure ◽  
Welded Joints ◽  
Power Plants ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Pipe Length ◽  
Welding Sequence ◽  
Weld Toe ◽  
Weld Fatigue

Fatigue failures of small bore piping systems have historically occurred in nuclear power plants, resulting in unanticipated plant downtime and substantial financial loss. If the failures were not caused by defects, the reasons of the initiation of fatigue cracks were not clear in many cases. This paper presented a set of weld fatigue response data which pointed to the strain ratcheting response as a probable reason for weld fatigue failure. A systematic set of low-cycle fatigue tests on butt- and socket welded piping joints in the cantilever set up is conducted. A new observation made in these tests is that the recorded strains near the weld toe ratchet continuously, which results in the initiation of fatigue crack(s). Comparison of these ratcheting responses with those from the cyclic bending of straight pipe and ratcheting experiments at the material level indicates that the residual stresses at welded joints may induce the ratcheting responses. This observation is further supported by the symmetric strain response (no ratcheting) at the mid-pipe length, which is located away from the welded joint. At this location, there are no residual stresses to induce ratcheting. It is observed that the fatigue cracks in all experiments occurred at the weld toe location where the ratcheting strain is the largest. The experimental data indicate that the fatigue life of materials is reduced in the presence of ratcheting. It is also observed that the ratcheting is influenced by the welding sequence. One interesting aspect of the weld fatigue data developed is that the ratcheting at the weld joints occurred under a displacement-controlled loading cycle. This study with its limited time and resource could not explore this issue. A plausible reason could be due to material heterogeneity at the welded joints.

Optimisation of a dosing strategy for an HC-SCR diesel exhaust after-treatment system

2002 ◽  
Vol 87 (2) ◽  
pp. 207-217 ◽  
Author(s):  
Björn Westerberg ◽  
Christian Künkel ◽  
C.U.Ingemar Odenbrand
Keyword(s):  
Diesel Exhaust ◽  
Treatment System ◽  
Dosing Strategy ◽  
Exhaust After Treatment

scholarly journals Fatigue Failure Analysis of Fillet Welded Joints Used in Offshore Structures

2014 ◽  
Author(s):  
Jonas W. Ringsberg ◽  
Majid Anvari ◽  
Djan Eirik Djavit ◽  
Erik Strande
Keyword(s):  
Fatigue Life ◽  
Fatigue Failure ◽  
Welded Joints ◽  
Parameter Study ◽  
Maritime Industry ◽  
Calculation Methods ◽  
Notch Stress ◽  
Weld Toe ◽  
Effective Notch Stress ◽  
Weld Root

This paper presents a comparison made of different fatigue calculation methods used in the maritime industry today, with the aim of having a higher control of a fatigue failure site. To provide an overview of the different fatigue calculation methods, a comparison study was performed, as well as a local weld parameter study for two typical fillet welded joints. The two methods used for this study were the structural hot spot and effective notch stress method. Two fillet welded joints were provided by Aker Solutions MMO AS, Bergen, Norway. The first joint is a rectangular hollow section from a davit, built as a truss. The second model is a part of a K-joint from a semi-submersible (Aker H3 design). Both joints were analysed using fine 3D finite element models. The two different fatigue life calculation methods yielded different fatigue lives for the weld toe, with inconclusive results regarding their conservatism which is discussed in the paper. An increased weld toe radius gave a higher fatigue life for the weld toe, while the larger weld size increased the fatigue life in the weld root. Any weld size effect regarding fatigue life in the weld toe could not be established. Based on the effective notch stress method calculations, there was an indication of weld root failure for the K-joint of the drilling unit. Fatigue life improvement methods only increasing weld toe fatigue life are not recommended based on these results.

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